This invention is generally directed to the use of specific toner and developer compositions, and more specifically, the present invention is directed to processes for generating images of outstanding consistent quality and reduced noise characteristics for substantially an unlimited number of imaging cycles with a two component magnetic developer composition. Specifically, there is provided in accordance with the present invention processes for generating prints of high quality with two component magnetic developer compositions that retain their triboelectric charging characteristics for in excess of 1.5 million imaging cycles. Also, the developer compositions selected for the present invention are useful for accomplishing the continuous unlimited development of electrostatic latent images. Thus, the two component designed developer compositions of the present invention are specifically useful in xerographic printing processes, inclusive of those embodied by the commercially available Xerox Corporation 9700.RTM., 9500.RTM. and 5600.RTM. imaging apparatuses. With these processes the prior art problem of obtaining outstanding developed images for extended time periods is eliminated when using the developer compositions of the present invention. Also, the unique two component developer compositions of the present invention possess stable triboelectric charging characteristics for the entire imaging sequence, a property not achievable with many of the compositions of the prior art. Further, there is reduced machine maintenance, and improved admixing with the developer compositions of the present invention. Moreover, in accordance with the process of the present invention, wherein the average diameter of the toner particles selected are from about 6 to about 10 microns there is obtained improved xerographic print quality with reduced background deposits. Additionally, use of the superior unique developer compositions of the present invention enable other outstanding characteristics as disclosed hereinafter.
Numerous prior art patents are in existence directed to magnetic toner compositions. For example, there is disclosed in U.S. Pat. Nos. 3,239,465 xerographic toner particles comprised of a resinous binder and a ferromagnetic material. Specific magnetic substances selected for the toner of this patent include magnetic iron, nickel iron alloys, nickel-cobalt-iron alloys, and magnetic oxides. One disadvantage associated with the magnetic toner composition of this patent, which problem is solved with the two component developer composition of this invention, resides in achieving more efficient transfer of the developed images for extended time periods. Also, the toner composition of this patent does not retain its charging properties for an extended number of imaging cycles.
Additionally, there is disclosed in U.S. Pat. Nos. 3,345,294 and 4,082,681, toner compositions with magnetic components therein. In the '294 patent there are illustrated toner compositions with certain resin particles, magnetic substances, inclusive of magnetic iron oxides, ferroferric oxide powders, and a magnetic metal, or an alloy. The '681 patent discloses magnetic developers with a magnetic material, and finely divided conducting substances such as conductive carbon black particles. Moreover, there is disclosed in U.S. Pat. No. 4,288,519 a dual purpose single component conductive magnetically attractive toner comprised of a mixture of thermoplastic resins, finely divided magnetic pigments, and conductive pigments, Also, there is described in copending application U.S. Ser. No. 566,754, the disclosure of which is totally incorporated herein by reference, two component developer compositions comprised of polyester toner resin particles, about 20 to 50 percent by weight of magnetite, and carrier particles consisting primarily of a steel core coated with a terpolymer resin.
The developer compositions of the referred to copending application enable smudge resistance images, and prevent unwanted deposition of toner particles in a xerographic imaging apparatus. Furthermore, disclosed in U.S. Pat. No. 4,517,268 are processes for generating documents, such as checks, with two component developer compositions comprised of magnetite, certain resin particles, and carrier particles consisting of ferrite cores coated with polymeric compositions, inclusive of terpolymer compounds.
Furthermore, there is disclosed in copending application U.S. Ser. No. 681,777, now U.S. Pat. No. 4,609,603 entitled Process for Achieving Consistent High Quality Images With Magnetic Developer, the disclosure of which is totally incorporated herein by reference, a process for generating consistent high quality images for extended periods, consisting essentially of (1) providing a xerographic imaging, or printing apparatus; (2) adding thereto a stable two component developer composition comprised of resin particles, first pigment particles, second magnetite pigment particles, which are present in a greater amount than the first pigment particles, and blended flow additive particles; and carrier particles consisting of a ferrite core or a steel core, and a coating thereover selected from the group consisting of terpolymers of styrene, methacrylate, and triethoxysilane; and polymethacrylate, which coating has incorporated therein conductive particles; (3) forming electrostatic latent images, or magnetic images in the apparatus; and (4) developing the images formed, wherein the developer composition retains its electrical properties for over 2.5 million imaging cycles. The process of the present invention is similar to that described in the aforementioned copending application with the primary exception that with this invention there are selected toner particles with an average diameter of 6 to 10 microns, contrary to the prior art which teaches that the elimination by size classification of toner particles with a diameter of, for example, less than 10 microns dramatically reduces process stability and developer life.
Therefore, while many of the prior art magnetic toner compositions are sufficient for their intended purposes, there remains a need for imaging processes with improved two component magnetic toners that enable a reduction in xerographic noise characteristics. Also, there is a need for stable two component developer compositions that will enable the generation of developed images with exceptional quality; and further that will maintain their triboelectric charging characteristics for substantially unlimited imaging cycles. Furthermore, there is a need for imaging processes with two component magnetic developers that have improved aging characteristics in xerographic printing systems. Aging, a prevalent problem in many xerographic imaging processes, involves, for example, a continuous reduction in toner charging capability, which eventually causes copy quality degradation as evidenced, for example, by excessive background printout. The use of the two component magnetic developer compositions of the present invention enables these difficulties to be eliminated in that aging is reduced significantly; and images of excellent quality are generated for substantially unlimited imaging and printing cycles.
Accordingly, the present invention enables xerographic imaging and printing processes with a two component magnetic developer composition that retains its triboelectric properties; and in particular its triboelectric charging values for an extended number of imaging cycles, exceeding 1.5 million, for example, while also preventing machine contamination, and thus enabling the production of consistent high quality images. In contrast, in many prior art processes with similar developer compositions, the triboelectric charge typically undesirably decays continuously up to from about 500,000 to 1 million imaging cycles. There is also reduced machine maintenance when using the developer compositions of the present invention, and increased copy quality maintainability. With the two component developer compositions of the present invention there is also decreased machine down time, an essential characteristic for users., Additionally, with the process and developer compositions of the present invention, the prior art problem of machine down time is also overcome. These and other needs are achievable with the process of the present invention wherein there is selected specific toner and developer compositions, and wherein the diameter of the toner particles are from about 6 to about 10 microns, thereby further enabling improved image quality.